Figure 7-17.-Typical beam and girder form.stripped and the bottom left in place until the concretehas hardened enough to permit removal of theshoring. The latter type of form is preferred, anddetails for this type are shown in figure 7-17.Although beam and girder forms are subjected to verylittle bursting pressure, they must be shored up atfrequent intervals to prevent sagging under the weightof fresh concrete.The bottom of the form should be the same widthas the beam and should be in one piece for the fullwidth. The sides of the form should be 1-inch-thicktongue-and-groove sheathing and should lap over thebottom as shown in figure 7-17. The sheathing isnailed to 2-by-4-inch studs placed on 3-foot centers.A 1-by-4-inch piece is nailed along the studs. Thesepieces support the joist for the floor panel, as shownin figure 7-18, detail E. The beam sides of the formare not nailed to the bottom. They are held in positionby continuous strips, as shown in detail E. TheFigure 7-18.-Assembly of beam and floor forms.7-9